The immune system is a defence mechanism of the organism having the function of protecting an organism from foreign attacks. The response known as the humoral response produces antibodies with a repertoire that is unique to each individual. However, the immune system, in particular the antibodies secreted by the humoral response, are the source of major risks when transplanting animal tissue or organs into human beings or during inter-human transfers (of blood, plasma or an organ).
Similarly, many auto-immune diseases are due to the perception by the organism of the organism's own protein, lipid, or saccharide determinants as being foreign, which generates a chronic immune response. Similarly, when pharmaceutical preparations containing antibodies are injected into an individual, it is vital that the corresponding antigen, if it is not the therapeutic target, is not present in the recipient in order to avoid the risk of causing an unwanted response; one example of such a response is hemolysis due to antibodies against the antigenic determinants of the blood groups. Thus, an injectable preparation must be free from that type of antibody.
To accomplish this, anti-protein antibodies have been purified for a long time, but purifying anti-saccharide antibodies is more problematic because of the difficulty of synthesizing the antigens (which are complex molecules resulting from a multi-enzymatic in vivo synthesis) and of the low affinity constant between the antibody and the antigen. This low affinity of the anti-saccharide antibodies leads to the presence of a very large excess of antigen compared with the antibodies that are to be eliminated from the medium (the excess is by a very large factor, i.e. 10000 to 100000 molecules of saccharide antigen for one molecule of antibody, this ratio being reduced if the oligosaccharide is bound onto a solid multimerized or polymerized phase). At the same time, the affinity of an IgM type antibody, which is a multimer with 10 possibilities for binding to the antigen via molecules, is higher than that for IgGs that only have two binding sites to the antigen. In the case of IgMs, this is known as avidity in order to take into account the synergistic effect of multiple antibody functions.
Thus, it is important to develop substrates multimerizing the saccharide antigens and to adapt them to the purification of IgGs as well as IgMs.
The separation of anti-saccharide antibodies, which are considered to be undesirable, from a biological liquid while conserving all of its properties, is a major therapeutic advance that has many applications.
During a blood transfusion, in order to be universal, the transfused plasma must be freed from antibodies that are known or assumed to be from the donor. Transfusions of biological liquids such as plasma are therapeutic acts for the purpose of obtaining regeneration of the hemostatic system or restoring the hemodynamics of the patient. The presence of antibodies from a donor with an incompatible group is tantamount to endangering the recipient patient by generating a hemolytic shock. The antibodies of blood groups present in the donor's plasma (anti-A, anti-B or both depending on the blood group) are determined by saccharide elements. In the current care system, a patient will only receive blood products that are identical to or compatible with that patient's blood group, giving rise to high logistical and storage costs. Proposing a plasma that is compatible with all patients would constitute a safe and economical solution.
Similarly, during a xeno-graft (i.e. a graft of an animal organ into a human), the antibodies against the determinants of the grafted organ must be eliminated in order to prevent massive rejection of the organ. Immunosuppressor treatment is a therapeutic solution to the problem, but suffers from secondary effects that can be life-threatening to the patient, and thus it is not entirely effective. Neutralization of the xeno-antibodies in the recipient by binding to the xeno antigens, which are saccharide compounds, constitutes an advantage in the field of xeno-grafts.
In autoimmune diseases, the excess of auto-antibodies may have important consequences. As an example, in Guillain Barré syndrome, the patient's auto-antibodies attack the patient's own nervous system and destroy the peripheral nerves (sometimes right up to the axon). It has been demonstrated that these antibodies become bound to gangliosides (which have a saccharidic antigen determinant) present in the nervous system. The motif that is recognised is also a saccharide. Being able to eliminate those elements that are not controlled from the immune system is an avenue for treatment of the syndrome.
More precisely, with blood transfusions, the key elements of the blood, red blood cells, platelets, and lymphocytes, carry A, B, or H saccharide antigens on their surface, which determine the blood group of individuals in a primate species. Individuals in blood group A have group A antigens; individuals in blood group B have group B antigens; individuals in blood group AB have both types of antigens. Individuals in blood group O carry the H antigen of which the oligosaccharide concatenation is found in group A and B antigens. A and B antigens have a supplemental monosaccharide. Group A antigens and group B antigens are also carried by various non-pathogenic infectious agents, essentially bacteria. Very early contact with such infectious agents brings about an immune response against the A or B determinant that the individual does not carry. Thus, individuals with blood group A mount a plasma response by generating anti-determinant B antibodies (also known as anti-B) and individuals with group B mount a plasma response by generating anti-determinant A antibodies (also known as anti-A); AB individuals do not have antibodies and those in group O have anti-A and anti-B antibodies. Blood group antibodies are essentially of the IgG and IgM type.
Plasma taken by plasmapheresis or from whole blood can only be used to treat patients after blood typing and plasma typing of the patients; this introduces a risk of errors, is time-consuming, and is a source of considerable logistical complexity.
In order to overcome this disadvantage, several solutions have been proposed. Mixing plasmas in defined proportions can dilute the concentrations of antibodies and can provide a mixture of antigens and antibodies that are mutually neutralizing (EP 0 896 824). However, that solution is only partial because the effective mixtures do not correspond to the frequency of the desired groups in donor populations. This solution is also risky since it leaves immune complexes in the treated plasmas, which are a potential source of autoimmune reactions.
A number of solutions also propose eliminating the antibodies from the plasma using group A or B-determinant antigenic oligosaccharides. One of the first to propose a solution of this type was Raymond U. Lemieux (U.S. Pat. No. 4,238,473 published in 1980). Since then, a number of approaches using chromatographic techniques in particular have been proposed, but have not been satisfactory in terms of efficiency and/or cost. The following may be cited in particular:                patent application EP 0 572 194, which describes a method of eliminating antibodies from a blood product while preserving the coagulation factors (see claim 1). To this end, a matrix is described that is constituted by a resin carrying antigens that may be bound by covalent bonding. Those antigens may be oligosaccharides. No detail is given as regards the modes by which the antigens are bound to the matrix;        U.S. Pat. No. 4,664,913, which describes a method of treating human plasma by passage through an immuno-adsorbing zone that is capable of binding both anti-A and anti-B antibodies. The antigen/substrate bond in the immuno-adsorbing zone is produced by reaction of an acyl azide function carried by the antigen on an aminated substrate. Reference is also made in that document both to U.S. Pat. No. 3,555,143, which describes particles carrying amine, carboxy, or hydroxy functions in order to bind to the antibodies, and also to U.S. Pat. No. 4,108,974, which describes beads carrying carboxylate for coupling with antibodies carrying amine functions;        document WO 2008/136735, which concerns a substance comprising at least one ligand, bound to a separation material, also termed a matrix, allowing for selective binding to a biomolecule or selective cleavage of a biomolecule. One of the applications for that product is its use to reduce the antibodies in a plasma or in a sample of whole blood. Binding to the matrix is envisaged via an NH2 function located at the end of the spacer arm located at the end of the saccharide, in particular on epoxy-activated agarose, tosyl-activated agarose, or a CnBr-activated matrix;        patent application EP 1 165 159, which describes a particular configuration of columns for the treatment of whole blood or of blood plasma, which contains a cross-linked matrix material to which at least one biologically active saccharide is covalently bound via at least one specific spacer. The binding mode described uses the reaction of an oligosaccharide carrying an —NH2 function at the end of the spacer arm on activated Sepharose-NHS. Other types of substrate of the epoxy-activated Sepharose type are cited. No other example of coupling is provided in the description;        patent application WO 2011/046504, which describes a product and a method for carrying out a treatment or a purification containing at least two filters or one filter and one centrifugation or two centrifugations and a component that contains at least one substance that is capable of binding to a target substance. It is pointed out that the ligand is bonded to the matrix in a covalent manner and that various methods selected by the person skilled in the art could be used. The binding mode detailed uses covalent coupling between an —NH2 function carried by the saccharide, and a carbonyl group present on the matrix in order to obtain an amide bond is described. It is also pointed out that the amide bond may be obtained by the EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide) reaction with a carboxyl group on the matrix that is activated in order to react with the saccharide derivative. A more precise example is not provided;        patent application EP 2 556 848, which describes a separation material comprising a saccharide bonded via a particular spacer arm to a matrix in order to be able to separate substances from a liquid. It is pointed out that the oligosaccharide-matrix bond may be obtained by reacting a compound on a matrix carrying —NH2, —N3, —COOH, —CHO, NH2—NH—, HC≡C—, or epoxy functions (see definition of F1 on page 4, line 7). The coupling reaction detailed in paragraph [0069] states that the bond is formed between a carboxyl group and an amine and that one of the methods conventionally used is the reaction of a carboxylic acid with a carbodiimide in order to facilitate its coupling with an amine in a manner such as to obtain an amide type bond. The substrates detailed in the examples exclusively incorporate epoxy, amino, and carboxylic acid functions.        
Thus, it appears that various solutions using antigenic oligosaccharides of a blood group grafted onto a substrate have been proposed. The oligosaccharide/substrate bond is usually produced on a substrate carrying —NH2, epoxy, or carboxylic acid functions.